This invention relates to pumps and pumping apparatus and in particular relates to pumps of that type which are used for transporting slurries, particularly slurries containing abrasive materials in a fluid in what is commonly called centrifugal pumps.
Slurries containing various fluids and abrasive particles, particularly slurries which need to be transported in the mining industry, are very destructive to pumps used to transport slurries. Centrifugal pumps commonly contain an impeller positioned in a pump casing which has an inlet defined by an axis common to the impeller. The slurry enters the casing and impeller along said axis and high speed rotation of the impeller changes the slurry flow direction 90 degrees into an annular outer pump chamber from which the slurry exits through a centrifugal pump outlet having an axis in a plane commonly positioned at right angles to the inlet axis and offset by approximately the radius of the pump. The portion of the pump which surrounds the inlet is commonly called the suction side liner and it is positioned a predetermined short distance away from the impeller suction side, the distance being so small as to substantially preclude slurry flow between the impeller and the suction side liner.
An abrasive slurry wears down the suction side liner adjacent the impeller, increasing the gap between the impeller and the suction side liner so as to permit slurry flow between the impeller and suction side liner and the irregular surface also causes irregular slurry flow patterns, the leakage and irregular flow reducing pump efficiency and causing premature pump failure.
Prior attempts at correcting suction side liner wear have been made, such as described in U.S. Pat. No. 4,527,948 issued July 9, 1985 to Graeme R. Addie in which a provision is made for periodically adjusting the axial position of the impeller by an adjustment screw so as to reduce the gap between the impeller and the suction side liner as wear takes place. Such a technique compensates for premature wear but does not prevent premature wear.
Highly wear resistant materials such as ceramics are in common usage in various industries, but ceramics are extremely expensive and difficult to make in large pieces due to manufacturing concerns such as high pressure required for the manufacturing process so less expensive materials have been in common usage in suction side liners, which continue to suffer excessive wear prematurely.